Hi @LMG, Lisa-Marie,
Interesting use case. Did you have a look to a dashboard widget to consolidate all your lower level plans? E.g. a dashboard timeline (which can be changed to day / week / month) views showing all tasks in the connected boards. Depending on your plan you might hit a maximum nr. of boards in a dashboard (PRO plan currently allows 10).
As an alternative to a dashboard view you could consider to use an app like the one I created (currently to consolidate statuses and numbers). See Monday app with automations released - #4 by basdebruin for more details. This app could be extended to use timelines but I am wondering if you want a consolidated timeline (like one timeline for all tasks in lower level plan) or if you want to show all (sub) task from you lower level boards.